How to download asset bundles and storing it locally in ios

I am doing a project that has a lot of assets to be downloaded at run time, So I am using asset bundles and storing them in the server. Now, I want to download these asset bundles and store it locally in my iOS device for the first time and should be able to run the game on offline mode when ever i open the game. Is this possible?? if yes, then how to do it?? Thanks